A charge pump circuit (voltage conversion circuit) functioning as a circuit that increases power supply voltage from an external power supply, which normally supplies power to a load circuit, to a desired voltage value is known (for example, refer to patent document 1).
FIG. 10 is a block diagram of a charge pump circuit 101, which is described in patent document 1. The charge pump circuit 101 includes a pumping circuit 102, an oscillation circuit 103, and a detector 104. The pumping circuit 102 charge-pumps power supply voltage. The oscillation circuit 103 generates a pulse signal for controlling the drive timing of the pumping circuit 102. The detector 104 detects an output potential of the pumping circuit 102. The pumping circuit 102 uses the rising and falling of the pulse signal formed by the oscillation circuit 103 to perform charge-pumping. Internal power, which is the output of the pumping circuit 102, is increased by a fixed voltage whenever charge-pumping occurs. The internal power is supplied to, for example, a load circuit. The detector 104 compares the potential of the internal power with a reference potential and outputs a pumping enable signal to the oscillation circuit 103 whenever the internal power potential becomes lower than a predetermined potential. The oscillation circuit 103 generates a pulse signal that oscillates in constant cycles in response to the pumping enable signal. The pumping circuit 102, which is driven by the pulse signal, increases the voltage of the internal power.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2000-40362